Learn About PC Virus

Learn About PC Virus

A computer virus is a potentially damaging computer program designed to affect, or infect, your

computer negatively by altering the way it works without your knowledge or permission. More

specifically, a computer virus is a segment of program code that implants itself in a computer file

and spreads systematically from one file to another. Viruses can spread to your computer if an

infected floppy disk is in the disk drive when you boot the computer, if you run an infected

program, or if you open an infected data file in a program.

Computer viruses, however, do not generate by chance. Creators, or programmers, of computer

virus programs write them for a specific purpose – usually to cause a certain type of symptom or

damage. Some viruses are harmless pranks that simply freeze a computer temporarily or display

sounds or messages. When the Music Bug virus is triggered, for example, it instructs the

computer to play a few chords of music. Other viruses, by contrast, are designed to destroy or

corrupt data stored on the infected computer. Thus, the symptom or damage caused by a virus

can be harmless or cause significant damage, as planned by its creator.

Viruses have become a serious problem in recent years. Currently, more than 45,000 known

virus programs exist and an estimated six new virus programs are discovered each day. The

increased use of networks, the Internet, and e-mail has accelerated the spread of computer

viruses, by allowing individuals to share files – and any related viruses – more easily than ever.

Types of Viruses

Although numerous variations are known, four main types of viruses exist: boot sector viruses,

file viruses, Trojan horse viruses, and macro viruses. A boot sector virus replaces the boot

program used to start a computer with a modified, infected version of the boot program. When

the computer runs the infected boot program, the computer loads the virus into its memory. Once

the virus is in memory, it spreads to any disk inserted into the computer. A file virus attaches

itself to or replaces program files; the virus then spreads to any file that accesses the infected

program. A Trojan horse virus (named after the Greek myth) is a virus that hides within or is

designed to look like a legitimate program. A macro virus uses the macro language of an

application, such as word processing or spreadsheet, to hide virus code. When you open a

document that contains an infected macro, the macro virus loads into memory. Certain actions,

such as opening the document, activate the virus.